1. Field of the Invention
The present invention relates to a membrane for separating gas, and more particularly, to a silica-like membrane for separating gas, and a method for forming.
2. Description of the Prior Art
Today, due to the trend of globalization, environmental issues constantly rise. Especially in the industry, carbon rights issues related to their research have been continuously discussed. Hence, in future industry trends, exhaust gas recycling or separation is in strong demand. In current industrial utility, the gas separation process has been applied in a wide variety of separation processes. In particular, the applications purifying O2 process from air, as the combustion process of carbon dioxide or oxy-fuel in the pre-combustion and post-combustion, which is more vigorously using a gas separation membrane. Using a thin-membrane separation process has a number of advantages which are: low cost, low energy consumption, and easy to operate.
In addition, a polymer membrane has advantages which are the excellent characteristics for forming the membrane, the excellent homogeneity, high regeneration, and simple preparation methods. Thus it is widely used in the development of a gas separation membrane. However, it has a poor effect for the selectivity and the gas flux for the polymer membrane in a large number of gas treatments, and thus it cannot be applied to a large number of treatments for industrial gas separation.
In the prior conventional art, there are two methods for the development of the gas separation membrane, one is a high throughput, low selection ratio, and the other is low throughput, high selection ratio. Thus, a porous inorganic membrane having a molecular sieve mechanism has been used in the gas separation procedures. It causes concern to the industry, which can provide better gas separating properties, which can be compared with the polymer membrane. Silica membrane is based on a single layer, porous inorganic membrane, having high permeability and high selectivity, but inorganic characteristics make the physical properties of the silica membrane to be brittle, and the process is complex and difficult to prepare. It is manufactured by the following universal methodologies: chemical vapor deposition (CVD) and sol-gel. Chemical vapor deposition (CVD) can be used to prepare uniform and ultrathin silica membrane, but it contains a number of steps, and thus the production cost is expensive; while the sol-gel (sol-gel) is a relatively low-cost manufacturing process, but the homogeneity of the silica membrane is poor. In order to improve the uniformity, it is repeated to coat a sol-gel on the substrate and calcine the substrate repeatedly; however, this procedure is very time-consuming.
Another low-cost approach to prepare a silica membrane is the oxidative thermolysis for a precursor of a rubbery membrane of polydimethylsiloxane (PDMS). In addition, there is another way to decompose a copolymer material at high temperatures, such as a precursor polyimide-PDMS to manufacture the microporous carbon-silica membrane for separating gas.
However, all the preparation methods described above, most of them are used with a pyrolysis technology in a high-temperature oven. It is time-consuming and expensive. Furthermore, there is another previous technology for reforming the membrane for separating gas by ultraviolet (UV), the selectivity of the membrane is improved. However, this method has a fairly lengthy preparation process, and limits the size for their preparation, so a large area cannot be formed at a time. Hence, it must be a single small region to form. Therefore, its manufacturing process is very time consuming.
Accordingly, the development of a low-cost, high selectivity, and high-throughput gas separation membrane is the major target which is being desperately developed in the industry.